1. Field of the Invention
This invention is directed toward an improved rolling firedoor.
Rolling firedoors are usually employed in commercial establishments to close large openings and comprise horizontally disposed metal slats hingedly joined together to form a closure. A drum is rotatably mounted in a horizontal position at the top of the opening. One end of the closure is fixed to the drum. Rotation of the drum in either direction winds or unwinds the closure on it, opening or closing the opening. When the closure is wound up to have the opening open, spring means associated with the drum, as are well known, provide enough tension to keep the drum from rotating under the unbalanced weight of the closure. Without the spring means, the closure would unwind and close the opening.
2. Description of the Prior Art
The drum is normally rotated by a chain drive operated from the floor below the drum. In case of a fire, the chain drive can be disconnected, the tension of the spring means reduced, and the closure will unroll off the drum under the influence of gravity to close the opening. A fusible link, melted by the heat of a fire, is used to automatically disconnects the chain drive from the drum, and to reduce the tension of the spring means to allow the closure to close. Braking means, usually in the form of a rocker escapement mechanism, are employed to control the rate of descent of the closure during a fire. These descent-rate control means are also usually made operative on the melting of a fusible link.
Examples of firedoors of the above type are shown in whole or in part in U.S. Pat. Nos. 2,564,208; 2,946,377 and 3,685,567, and in Canadian Pat. No. 1,088,580 by way of example.
A common problem with the known firedoors is that once the fusible link is broken, and the closure is automatically lowered, the closure cannot be raised again until the chain drive is reconnected to the drum. In known doors, this involves having a person climb up to the drum to reconnect the chain drive to the drum. A ladder is needed which can be hard to find in an emergency situation.